The present invention relates to catalysts. More particularly, the present invention relates to such novel catalysts containing a cyclopentadienyl zirconium complex and an organo aluminum compound. Such catalysts are particularly useful for the preparation of polymers of vinyl aromatic monomers having a high degree of syndiotactic molecular structure.
It is previously known in the art to prepare polystyrene having a high degree of syndiotacticity by polymerizing styrene monomer in the presence of a catalyst containing a titanium compound and an aluminum organo compound. This work has been reported by N. Ishihara, et al., in Macromolecules, 19, Page 2464-2465 (1986).
The same researchers later reported that zirconium based catalysts, specifically ZrCl.sub.4, and biscyclopentadienyl zirconium dichloride in combination with polymethylaluminoxane gave only atactic polystyrene, Polymer Preprints (Japan), vol. 36, No. 2 May 12, 1987.
In EPO No. 210,615 syndiotactic polystyrene polymers were prepared utilizing titaniumtetraethoxide, and oyclopentadienyltitaniumtrichloride complexes in combination with a polymethylaluminoxane cocatalyst.